UPDATE 1:40 PM: AMC just issued a statement confirming that Hell On Wheels showrunner John Shiban has left and that the series’ third season renewal is now contingent on hiring a new showrunner approved by the network. In a statement, Shiban called the departure “a difficult decision.” Read both statements below my original post:

EXCLUSIVE 11:50 AM: There is some behind-the-scenes drama on AMC‘sHell On Wheels. The Western drama on Monday was given a 10-episode third-season renewal, but it was picked up without its creators/executive producers Joe and Tony Gayton, who left their day-to-day duties on the show when their contract was not renewed. (They may consult.) At the time, AMC said John Shiban would continue as executive producer/showrunner. Now I hear that veteran showrunner Shiban has informed the network that he won’t be coming back after two years on the show. As a result, I hear Hell On Wheels‘ pickup has been put on hold until a new showrunner is found.

This is the latest AMC series hit by major creator/showrunner departures. The Walking Dead‘s Frank Darabont left in Season 2, Rubicon creator/exec producer Jason Horwitch exited during production on its first and only season, and Hell On Wheels now is looking to continue without its creators and showrunner. Before joining Hell On Wheels, The X Files alum Shiban worked as a consulting producer on another AMC series from a former X Files writer-producer, Vince Gilligan’s Breaking Bad.

Hell On Wheels wrapped its second season earlier this month with a solid average of 2.4 million viewers. That was down from the average of 3 million viewers for the show’s freshman season — but this time around, Hell On Wheels did not have blockbuster The Walking Dead as a lead-in and was impacted by the lack of AMC carriage on Dish Network. Hell On Wheels, from Entertainment One and Endemol USA, is exec produced by Jeremy Gold and David Von Ancken.

AMC: John Shiban has informed AMC, Entertainment One and Endemol that while he was fully on board when the network informed him about their intent to pick-up Hell on Wheels, he has since made the personal decision that he will be unable to return as showrunner. He has asked the production partners to seek a replacement showrunner. Like all of our shows, network pick-ups are always conditioned on an approved showrunner. We are confident that eOne and Endemol will satisfy that obligation in the near future.

John Shiban: I’m very proud of our work on HELL ON WHEELS and was thrilled to hear the show would have a Season Three. I have since made the difficult decision that the time has come for me to leave. I care deeply about the series and will do whatever I can to aid in the transition to ensure the continued success of the show. I truly value all the time I have spent with this wonderful group of very talented people.